Focus on the New Network Edge, the Server

For decades we’ve protected the enterprise at the network edges where the Internet meets our DMZ, and then again where our DMZ touches our Intranet. These two distinct boundary layers and the DMZ in-between makeup what we perceived as the network edge. It should be pointed out though that these boundaries were architected long before phishing and click-bate existed as part of our lexicon. Today anyone in the company can open an email, click on an attachment or a web page, and open Pandora’s box. A single errant click can covertly launch a platform that turns the computer into a beachhead for the attacker. This beachhead then circumvents all your usual well-designed edge focused defenses as it establishes an encrypted tunnel enabling the attacker access to your network whenever they like.

Once an attacker has established their employee hosted beachhead, they then begin the search for a secondary, server-based, vantage point from which to operate. A server affords them a more powerful hardware system and often one with a higher level of access across the entire enterprise. Finally, if the exploit is discovered in that server, the attacker can quickly revert to their fall back position on their initial beachhead system and wait out the discovery.

This is why enterprises must act as if they’ve already been breached. Accept the fact that there are latent attackers already inside your network seeking out your corporate jewels. So how do you prevent access to your companies most valuable data? Attackers are familiar with the defense in depth model so once they’re on your corporate networks, often all that stands between them and the data they desire is knowing where it is hidden, and obtaining the minimum required credentials to access it. So how do they find the good stuff?

They start by randomly mapping your enterprise network in hopes that you don’t have internal honey-pots or other mechanisms that might alert you to their activity. Once the network is mapped they’ll then use your DNS to assign names to the systems they’ve discovered in hopes that this might give them a clue where the good stuff resides. Next, they’ll do a selective port scan against the systems that look like possible targets to determine what applications are running on them to fill in their attack plan further. At this point, the attacker has a detailed network map of your enterprise, complete with system names, and the names of the applications running on those systems. The next step will be to determine the versions of the applications running on what appear to be the most critical systems, so they’ll know which exploits to leverage. It should be noted that even if your servers have a local OS based firewall, you’re still vulnerable. The attackers at this point know everything they need to, so if you haven’t detected the attack by this stage, then you’re in trouble because the next step is the exfiltration of data.

If we view each server within your enterprise as the new network edge, then how can we defend these systems? Solarflare will soon announce ServerLock, a system that leverages the Network Interface Card (NIC) in your server to provide a new defense in depth layer in hardware. A layer that not only shields it from attack, but it can also camouflage the server and report attempts made to access it. Two capabilities not found in OS based software firewalls. Furthermore, since all security is handled entirely within the NIC, there is no attackable surface area. So how does ServerLock provide both camouflage and reporting?

When a NIC has ServerLock enforcement enabled only network flows for which a defined policy exists are permitted to enter or exit that server. If a new connection request is made to that server which doesn’t align with a security policy, say from an invalid address or to an invalid port, then that network packet will be dropped, and optionally an alert can be generated. The attacker will not receive ANY response packet and assume that nothing is there. Suppose you are enforcing a ServerLock policy on your database servers which ONLY accepts connections from a pool of application servers, and perhaps two administrative workstations, on specific numeric ports. If a file server were compromised and used as an attack position once it reaches out to one of those database servers via a ping sweep or an explicit port scan it would get NOTHING back, the database server would appear as network dark space to the file server. On the ServerLock Manager console alerts would be generated, and the administrator would know in an instant that the file server was compromised. Virtually every port on every NIC that is under ServerLock enforcement is turned into a zero-interaction honeypot.

So suppose the attacker has established themselves on that file server, and the server then gets upgraded to ServerLock and put under enforcement. The moment that attacker steps beyond the security policies executing in that NIC on that server the jig is up. Assuming they’re on the server, once they attempt any outbound network access that falls outside the security policies those packets will be dropped in the NIC, and an alert will be raised at the ServerLock Management console. No data exfiltration today.

Also, it should be noted that ServerLock is not only firmware in the NIC to enforce security policies, but it is also an entire tamper-resistant platform within the NIC. Three elements make up this tamper-resistant platform, first only properly signed firmware can be executed, older firmware versions cannot be loaded, and any attempt to tamper with the hardware automatically destroys all the digital keys stored within the NIC. Valid NIC firmware must be signed with a 384-bit key utilizing elliptic curve cryptography. The Solarflare NIC contains the necessary keys to validate this signature, and as mentioned earlier tampering with the NIC hardware will result in fuses blowing that will corrupt the stored keys forever rendering the both unusable and unreadable.

Today enterprises should act as though they’ve already been compromised, and beef up their internal defenses to protect the new network edge, the server itself. In testing ServerLock, we put a web server protected by ServerLock directly on the Internet, outside the corporate firewall.